1. Technical Field
The subject matter of the present disclosure relates to the illumination arts, lighting arts, solid-state lighting arts, and related arts.
2. Description of Related Art
Lighting fixtures including recessed lighting fixtures can use a floodlight bulb for general lighting tasks, a spotlight bulb that produces a relatively narrow beam of intense light, or other lamps for directional lighting. These directional lamps are useful to highlight a subject or an otherwise unlit area. Conventionally, the prior art utilizes individual imaging optical elements including lenses, reflectors, and total-internal-reflection (TIR) optics or combinations thereof to form the light emitted from the light source into a beam. These imaging elements are typically designed with a single focal point in order to perfectly collimate the light coming from an idealized point light source located at the focal point. Alternatively, selected examples of prior art instead utilize optical elements designed with more than one focal point, however, these focal points are still located along the optical axis.
A problem associated with these types of imaging optical systems is that any positional non-uniformities in the light source itself, either with respect to color or luminance, are directly translated into the light beam. These non-uniformities can be present in virtually all types of sources including incandescent, halogen, fluorescent, HID, and solid-state light sources. As a result, when the beam is directed onto a surface, these non-uniformities are projected onto the surface as well, resulting in a visually unappealing appearance of the light beam. To prevent this from occurring, diffusive elements such as lenslet arrays, holographically patterned films, and even surface roughened materials are introduced into the optical system to smooth out the non-uniformities in the light beam. Alternatively, some degree of diffusion can be achieved by slightly moving the source away from the focal point of the optical system. In either case, however, the added diffusion also serves to widen the overall light beam making it very difficult to efficiently form the narrow, intense beams desired for many applications. Thus, the improvement in visual appearance resulting from the added diffusion comes at the cost decreased optical performance.